Explanation:
In October of 1846,
William Lassell
was observing the newly discovered planet
Neptune.
He was attempting to confirm his observation, made just the previous week,
that Neptune had a ring.
But this time he discovered that Neptune had a satellite as well.
Lassell soon proved that the ring was a product of his new
telescope's distortion, but the satellite
Triton
remained.
The above picture of
Triton
was taken in 1989 by the only spacecraft ever to pass
Triton:
Voyager 2.
Voyager 2 found fascinating terrain,
a thin atmosphere, and even evidence for
ice volcanoes
on this world of peculiar orbit and spin.
Ironically, Voyager 2 also confirmed the existence of
complete thin rings around Neptune
- but these would have been quite
invisible
to Lassell!